1. Field of the Invention
This invention relates generally to detection systems or circuits, and more particularly, to an apparatus including an integrated digital counting circuit for measuring the amount of thread remaining on a sewing machine bobbin and generating signal when the amount of remaining thread is equivalent to that which is necessary to complete only one more seam.
2. Description of the Prior Art
As is well known, commercial sewing machines require first and second sources of thread. The first is generally mounted on the upper part of the machine and is threaded to engage the hook. This source of thread is visible to the operator. The second source of thread, contained in a bobbin, is housed beneath the slide plate or sewing surface for engaging the hook on the underside of the garment being sewn. The bobbin is inserted into a bobbin case which is in turn housed in a bobbin basket. Since the bobbin basket is mounted in the hook apparatus below the sewing surface, the amount of thread remaining on the bobbin is not readily apparent to the sewing machine operator. Thus, each time the sewing machine operator begins a new seam, he runs the risk of running out of bobbin thread before the seam is completed.
To require the operator to perform the manual manipulations necessary to visibly check the amount of remaining bobbin thread would be at least troublesome, and in a commercial setting, economically prohibitive. At the same time, however, to ignore the amount of remaining bobbin thread would require the operator to either rip out an incomplete seam or to pass on the garment bearing an incomplete seam as a "second" or "irregular."
Thus, while modern sewing machine technology enables operators to rapidly sew many seams, the operator has not yet been supplied with a convenient method or apparatus for monitoring the amount of thread remaining on the bobbin.